sound/usb: call usb_autopm_get_interface() for devices that should not

be suspended

Webcams with microphones are composite devices, and autosuspend is set
at the device level. If uvcvideo is probed after snd-usb-audio, the effect
of the quirk applied by snd-usb-audio is undone by uvcvideo's global
application of autosuspend.

Incrementing the interface's PM refcount in such cases prevents runtime PM
from happening, thus the device is left active.

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 1764b93..fbbe330 100644 (file)
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -817,8 +817,14 @@ static int usb_audio_probe(struct usb_interface *intf,
        if (ignore_ctl_error)
                chip->quirk_flags |= QUIRK_FLAG_IGNORE_CTL_ERROR;
 
-       if (chip->quirk_flags & QUIRK_FLAG_DISABLE_AUTOSUSPEND)
+       if (chip->quirk_flags & QUIRK_FLAG_DISABLE_AUTOSUSPEND) {
+               /*
+               * Grab the interface, because on a webcam uvcvideo may race
+               * with snd-usb-audio during probe and re-enable autosuspend.
+               */
+               usb_autopm_get_interface(intf);
                usb_disable_autosuspend(interface_to_usbdev(intf));
+       }
 
        /*
         * For devices with more than one control interface, we assume the